Flash device with compensation for ambient conditions such as temperature

ABSTRACT

A flash device for a camera comprising a main capacitor charged by a power source, a flash circuit for illumination of a flash lamp and a detector circuit, said detector circuit being thermally compensated for thermal variation of the flash device.

O UnIted States Patent 1151 3,688,659 Takishima et al. Sept. 5, 1972 [54] FLASH DEVICE WITH [58] Field ofSeaI'ch....95/l1.5 R, 11 R, 10 C, 10 CT, COMPENSATION FORAMBIENT 95/64 R; 240/ 1 .3; 5/241 P; 7/247 CONDITIONS SUCH AS TEMPERATURE [56] References Cited [72]- Inventors: Yoshiyuki Takishima; Yukio UNITED STATES PATENTS bah Japan 2,894,174 7/1959 Schankler ..315/241 P [73] Assignee: Canon Kabushiki Kaisha, Tokyo, 3,295,424 1/1967 Biber ..95/10 CT Japan V 3,257,607 6/1966 Pintell ..317/247 X i N 1970 FOREIGN PATENTS OR APPLICATIONS 21 Appl. No.: 93,595 1,291,192 3/1969 Germany ..95/53 EB 30 F A P Primary Examiner-Samuel S. Matthews orelgl? Pp nomy Data Assistant Examiner -Robert P. Greiner Dec. 1, 1969 Japan.... ..44/114200 .AtomeyMcGlew Dec. 1, 1969 Japan ..44/114199 TR Oct. 2, 1970 Japan ..45/98496 [57] ABS CT Oct. 2, 1970 Japan ..45/ 98495 A flash device for a camera comprising a main capacil tor charged by a power source, a flash circuit for illu- 52 us. c1 ..95/11 R, 95/115, 95/10 CT, miHafiO" of a flash lamp and a'detecmr circuit Said 240/13, 315/241 P detector circuit being thermally compensated for thers 1 Int. Cl. ..-...G03b 15/05, H05b 41/00 ma! vamtm 0f the flash devlce- 22 Claims, 14 Drawing Figures FLASH DEVICE WITH COMPENSATION FOR AMBIENT CONDITIONS SUCH AS TEMPERATURE The invention relates to a flash device with provision to correct the reduction of the amount of illumination caused by a reduction in the ambient temperature.

In general, a flash device includes a main capacitor as a storage source for luminous energy. It is desired that the main capacitor has a large capacity and a high voltage withstanding capability, and is yet small in size. To meet these requirements, an electrolytic capacitor is normally used in the flash device. However, an electrolytic capacitor has an electrostatic capacitance which is highly dependent upon the temperature, in particular on a temperature below C.

By way of example, FIG. 1 shows the temperature characteristics of electrolytic capacitors using glycerin (curve G) and ethylene glycol (curve E), respectively.

When such an electrolytic capacitor having a positive temperature coefficient is used as the main capacitor of a flash device, it will be understand that the energy E stored in the main capacitor, which is represented in the form E CV /2, 'where C denotes the capacitance and V the terminal voltage, varies as a function of the capacitance C, assuming a constant value for the terminal voltage, when the ambient temperature varies. Because the energy has a direct connection with the amount of illumination provided by the flash device, it results that the latter varies with a change in the ambient temperature.

Where a picture is taken by flashlight, using a flash device, the usual practice is to determine the diaphragm aperture by dividing the given guide number (equivalent to the amount of illumination) of theflash device with a distance to an object being photographed. Thus, if the actual guide number of the flash device is reduced on account of low temperatures, such practice will result in an underexposure.

Therefore, it is a primary object of the present invention to provide a flash device which is interlocked with a photographic camera and compensates for the reduction in the amount of illumination provided from the flash device itself that is caused by a reduction in temperature.

It is another object of the present invention to provide a flash device which is adapted to indicate a reduction in the amount of illumination.

It is a further object of the present invention to provide a flash device provided with an exposure indicator which is to be used to compensate for a reduction in the amount of illumination.

For better understanding of the present invention, several embodiments thereof will be described below with reference to the drawings, in which:

FIG. 1 is a graph which shows the variation of capacitance of an electrolytic capacitor on the ordinate as a function of ambient temperatures on the abscissa showing thermal characteristics of an electrolytic capacitor using glycelin (curve G) and ethylene glycol (curve E).

FIG. 2 is a circuit diagram of a first embodiment of the flash device according to the invention.

FIGS. 3a to 3f show partial modifications of the embodiment shown in FIG. 2.

FIG. 4 is a circuit diagram of a second embodiment of the flash device according to the invention.

FIG. 5 is a circuit diagram of a thirdembodiment of the invention.

FIG. 6 is a schematic view illustrating an exposure indicator to be used with the third embodiment of FIG. 5.

FIG. 7 is a circuit diagram of a fourth embodiment of the invention. 7

FIG. 8 is a circuit diagram of a fifth embodiment of the invention.

' FIG. 9 is a schematic view of an exposure indicator for automatically indicating the value of compensated exposure.

Referring to the drawings, and more particularly to FIG. 2 which shows a first embodiment of the invention, this embodiment includes a flash device 1 and a temperature compensating means 2 which are integrally constructed. The output information from the temperature compensating means 2 controls an indicator means 3, such as an exposure ammeter, provided in a photographic camera which is indicated by a block 4, and it is assumed that the camera 4 includes an electronic eye mechanism which determines the amount of exposure depending upon the indication provided by the means 3. The flash device 1 shown in FIG. 2 is essentially the same as that disclosed in a pending patent application Ser. No. 27,699 filed Apr. 13, 1970. In FIG. 2, a reference character F denotes a flash tube circuit including a trigger circuit. Numeral 101 denotes a discharge tube, 102 a trigger coil and 103 a resistor for charging a trigger capacitor 104. A variable resistor 105 is connected in parallel with a main capacitor 106. Reference character P denotes a power circuit. Numeral 107 denotes a power source, 108 a transistor, 111 a transformer having a feedback winding 109, primary winding and secondary winding 112, and 113 a rectifier element. Reference character Sw denotes a power switch which is interlocked with a switch in an electronic eye circuit to be described later in such a manner that when the power source 107 is turned off, the electronic eyecircuit is disconnected from the control of the flash device 1.

The temperature compensating means 2 includes the above-mentioned resistor 105, a neon discharge tube 115, a transistor 114, and diodes 118, 119 and 120. The transistor 114 has its base connected through the neon tube 115 with the movable point on the variable resistor 105, its collector connected with the power source 107, and its emitter connected with a resistor 116 and a sensitivity element 117, such as a thermistor having a negative characteristic, the other end of the sensitivity element 117 being connected with the base of the transistor 114. The temperature compensating means 2 further includes a variable resistor 121 for correcting the voltage drop across the emitter resistor 116, a diode 122 for obtaining a constant voltage and a biase resistor 123 for applying a predetermined voltage across the diodes 122 and 120. The diodes 118, 119 and serve to compress" the variation in voltage across the main capacitor 106 and to compensate for the rising time of the voltage across the base and emitter of the transistor 1 14.

Reference numerals 125, 126 designate a diode for protecting the diodes 122, 120 and the transistor 114 from the reverse voltage.

The output from the temperature compensating means 2 is derived from the junction between the transistor 1 14 and the emitter resistor 1 16.

The indicator means 3 is shown in the form of an electronic eye circuit, which includes an adjustable resistor 127 for adjustment with the film sensitivity, an ammeter 128 connected in parallel with the resistor 127, a power source 129 connected in series with a photo-conductor element 130 across the ammeter 128, and a resistor 131 connected in the input path from the temperature compensating means 2. A synchronizer switch 132 is adapted to be closed in synchronism with the full opening of the shutter blades. A switch SW is interlocked with'the switch SW in the power circuit P of the flash device.

The operation of the above embodiment will be described below briefly (For detailed description, refer the pending patent application Ser. No. 27,699 filed Apr. 14, 1970.).

With the closure of the power switch SW1, which is interlocked with the switch SW and of the switch 133, the main capacitor 106 starts to be charged through the diode 113. The voltage across the main capacitor 106 is detected through the movable point on the resistor 105, and it rises to a level which is high enough to cause an illumination of the flash discharge tube 101, the neon lamp 115 is illuminated, whereupon the voltage across the main capacitor is applied to the base of the transistor 114. This voltage applied to the base is variable by the action of the temperature sensitive element 117 that is connected across the base and emitter and has a resistance which varies in accordance. with the temperature. This means that the output resistance of the transistor 114 varies in dependence upon the temperature, if supposing the voltage across the main capacitor remains unchanged. As a consequence, the output from the temperature compensating means 2 contains an information concerning the temperature characteristic of the main capacitor 106, and the ammeter 128 operated by this output provides an indication of the diaphragm aperture which exactly correspond to the amount of illumination provided by the flash device.

FIGS. 3a to 3f show exemplary modifications of the first embodiment shown in FIG. 2. While the sensitivity element 117 is connected across the base and emitter of the transistor 114 in FIG. 2, it may be connected with the base, emitter or collector of the transistor 114, as shown in FIGS. 3a, 3b and 3c, respectively. FIGS. 3d, 3e and 3f illustrate the use of a silicon controlled rectifier SCR in place of the transistor 114. When such silicon controlled rectifier SCR is used, the sensitivity element 117 can be connected either in the input or output circuit, as shown in FIGS. 3d, 3e or 3f.

; FIG. 4 shows a second embodiment of the flash device 1 according to the invention. In this embodiment, a change in the amount of illumination which is caused by a change in the capacitance of the main capacitor in a flash device is conveyed through the temperature compensating means 2 to an indicator means 31 disposed in the flash device, which provides an indication for manually adjusting the diaphragm aperture of the camera 4. Specifically, connected in parallel with the main capacitor 106 is an ammeter circuit which comprises a resistor 202, an ammeter 201 having a guide number scale (not shown), and a temperature sensitive element 117 such as a thermistor. When the temperature falls, the thermistor operates to control the current flow through the ammeter 201 in a manner such that it corresponds to the capacitance of the main capacitor l06, thereby presenting a proper indication on the guide number scale. This guide number indication can be utilized to decide a diaphragm aperture for obtaining a proper exposure.

FIG. 5 shows a third embodiment of the invention.

Resistors R,, R and R are connected in series across where R denotes the resistance of the temperature sensitive element 117, and that under lower temperatures, which cause a change in the value of R,,,, the following relationships apply:

Consequently, under normal temperatures, as the main capacitor 106 is charged and the voltage thereacross reaches a given value, the voltage at the junction between the resistors R and R becomes higher than the voltage at the junction between the resistors R, and R so that one of the neon lamps, 301, is illuminated. Under lower temperatures, the voltage relationship is reverse, and the neon lamp 300 is illuminated. Whenever one of the neon lamps is illuminated there is a voltage drop across the resistor R.,, which serves the interruption of the charging of the main capacitor 106 by the power circuit P.

With the illumination of ether one of the neon lamps 300 and 301, the exposure indicator shown in FIG. 6 is actuated.

FIG. 6 shows an indicator device schematically, which is substantially similarly constructed as usual exposure indicators. Numeral 400 denotes an indicator needle, 401 a distance scale, 402 a window for setting film sensitivity and 403 a diaphragm aperture scale which is interlocked with the needle 400. The abovementioned neon lamps 300 and 301 are located on the back of the diaphragm aperture scale 403 and spaced apart by a distance corresponding to one diaphragm aperture value graduation. When taking pictures under normal temperatures, the distance scale 401 is rotated to a position corresponding to a given film sensitivity (which is ASA in the example shown). Then the diaphragm aperture scale 403 is rotated to cause the needle 400 to align with a desired distance graduation on the distance scale 401 which graduation corresponds to the distance to an object being photographed. Upon completion of the charging of the main capacitor 106, the neon lamp 301 is energized to illuminate a diaphragm aperture value graduation on the diaphragm aperture scale 403 which is on top of the neon lamp 301, this value graduation being F 2.8 in the example shown. Under lower temperatures, the neon lamp 300 will be energized to illuminate the value graduation which is the next lower value graduation on the scale 403 than the value graduation'illuminated by the neon lamp 301. The illuminated diaphragm value graduation is used to set the diaphragm aperture of the camera 4, whereby a proper exposure corresponding to the amount of illumination from the flash device is obtained. When a thermistor R, having a positive characteristic is used in this embodiment, the resistors in the voltage divider circuits should be chosen to satisfy the following relationships:

for lower temperatures. In this instance, the positions of the neon lamps shown in FIG. 6 must be interchanged.

. FIG. 7 shows a fourth embodiment of the invention. Resistors R and R are connected in series across the main capacitor 106. Also resistors R R and R are connected in series across the main capacitor 106. Numeral 500 denotes a transistor having its base connected with the junction B between the resistors R and R through a neon lamp 501. The collector and emitter of this transistor are connected across the resistor R so as to short out this resistor upon conduction of the transistor 500. A neon lamp 502 is connected across the resistors R and R the junction between the resistors r, and R being denoted by reference character A. A temperature sensitive element 1 17 is connected in series between the main capacitor 106 and the voltage divider circuits R to R These resistors are chosen so that they satisfy the following relationships:

R1=R9, and

The power unit P provides an output which charges the main capacitor 106, and when the voltage across the main capacitor reaches a given value, the neon lamp 592 is initially energized to illuminate a proper diaphragm aperture value under this condition (for example, F 2.8) on the exposure indicator of FIG. 6. As the main capacitor 106 continues to be charged to have a higher terminal voltage, the neon lamp 501 is illuminated, whereupon the transistor 500 is turned on to short out the resistor R whereby the potential at the point A falls and the neon lamp 502 is extinguished. Thus the lamp 501 indicates a proper exposure value (for example, F 2.0). Under lower temperatures, the

thermistor 117 will have an increased resistance to' decrease the potential at the point A or B in the respective voltage divider circuits, so that either neon lamp will not be illuminated until the voltage across the main capacitor reaches a higher value as compared with the value under normal temperatures. In this manner, there is provided an automatic compensation of a variation of guide number caused by a change in the ambient temperature when the neon lamp provides an indication, so that such indication can be used to decide a proper diaphragm aperture to assure a proper exposure.

FIG. 8 shows another embodiment of the invention which employs a thermistor having a positive characteristic. As shown, resistors R and R and a thermistor R, having a positive characteristic are connected in series across the main capacitor 106. Numeral 600 denotes a transistor having its base con nected with the junction between the resistors R and R through a neon lamp 601. The collector and emitter of the transistor 600 are connected so as to short out the series connection of a resistor R and the thermistor R, upon conduction of the transistor 600. A neon lamp 602 is connected with the junction between resistors R and R Numeral 603 denotes a rectifier element which is connected between the thermistor R, and the resistor R in order to prevent the influence of the transistor 600 upon the neon lamp 601. The resistors satisfy the following relationships:

As the main capacitor 106 is charged and the voltage drop across the resistors R R R, reaches a volt age which is sufiicient to illuminate the neon lamp 602, this lamp is illuminated. As the main capacitor is further charged, the neon lamp 601 is illuminated, whereupon the transistor 600 conducts. When the transistor 600 conducts, the resistor R and the thermistor R, are short-circuited to extinguish the neon lamp 602. Under lower temperatures, the thermistor R, will have a reduced resistance, so that the neon lamps 601 and 602 will be illuminated at higher voltages across the main capacitor 106 than those under normal temperatures. Such increased voltage can be made so as to correspond to a variation in the amount of illumination from the flash device, thereby enabling a proper exposure to be obtained.

FIG. 9 shows an embodiment which uses an exposure indicator as compensation means directly and utilize the indication provided to decide the diaphragm aperture of the camera. Numeral 401 denotes a rotatable distance scale having a window 402 for setting ASA sensitivity, and numeral 700 denotes an ASA scale fixed on a shaft 701. Numeral 403 denotes a diaphragm aperture scale which is adapted to rotate by elongation and contraction of a bimetal 704. This exposure indicator is arranged so that the diaphragm aperture scale rotates automatically in response to a change in temperature, thereby providing a scale correction, and thus, when taking pictures by flash light, the camera may be set according to the indication provided by the exposure indicator, without regard to an ambient temperature, and thus a proper exposure is obtained.

What is claimed is:

1. A flash device for a camera comprising a flash circuit including a main capacitor to store illumination energy and a dischargetube which illuminates in correspondence to the amount of illumination energy stored in the main capacitor, and indicator means coupled to said circuit for indicating the amount of the illumination of the discharge tube, said indicator means including compensating means varying in value according to the variation in the energy storing capability of said capacitor in response to an ambient condition and varying the indication of said indicator means on the basis of the ambient condition.

2. A device as in claim 1, wherein said value varies in response to temperature and said compensating means includes a temperature compensating element.

3. A device as in claim 1, wherein said indicating means includes means for detecting the illumination of energy charged across the main capacitor and an indicator, and wherein said compensating means is coupled between said detecting means and said indicator.

4. A device as in claim 1, wherein said indicating means includes a dial and a pointer, said compensating means includes a thermally deformable element, said indicating means connecting said compensating means to said dial and pointer for changing the positions of the dial and the pointer in correspondence with variation of atmospheric temperatures.

5. An apparatus as in claim 1, wherein said indicating means includes detecting means having a semiconductor element, and said compensating means includes a thermally compensating resistor coupled to said semiconductor element.

'6. A device as in claim 5, wherein said semi-conductor element is a transistor connected to said resistor.

7. A device as in claim 5, wherein said semi-conductor element is a silicon controlled rectifier connected to said thermally compensating resistor.

8. A device as in claim 5, wherein said indicating means includes a current meter, said compensating means being connected to said current meter so as thermally to compensate for the reading of said current meter.

9. A device as in claim 5, wherein said indicating means includes a lamp, the operation of said lamp being thermally compensated by said compensating means.

10. A device as in claim 9 wherein said indicating means includes a plurality of lamps, said indicating means including illuminating means for illuminating the lamps, said compensating means being connected to said illuminating means for varying the illumination of said lamps on the basis of thermal compensation.

1 1. A photographic system, comprising a flash circuit including a main capacitor to store illumination energy and a discharge tube which illuminates in correspondence to the amount of the illumination energy stored in said capacitor, indicating means coupled to said circuit for indicating the amount of the illumination of the discharge tube, and thermal compensating means coupled to said main capacitor and said indicating means to vary in value according to variation in temperature at the same rate as the temperature of said capacitor varies, a camera having exposure control means, said exposure control means being coupled to said indicating means to react therewith.

12. A photographic system comprising a main capacitor to store illumination energy, a flash circuit including a discharge tube which illuminates in correspondence to the amount of illumination energy stored in the main capacitor, a detecting circuit for detecting the terminal voltage of said capacitor, a camera, an exposure control circuit in the camera connected to said detecting circuit, vand compensating means for compensating for changes in illumination energy stored in the capacitor due to changes in atmospheric temperature, said compensating means being connected to said detecting circuit.

13. A photographic system as in claim 12 wherein said exposure control circuit includes an adjustable member, said adjustable member being coupled to said detecting circuit.

14. A power-source actuated flash device for a camera, comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable valve in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said compensating means including a transistor and a thermally compensating resistor connected therewith.

15. A power-source actuated flash device for a camera, comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means-for compensating for the thermal variations in the value, said compensating means including a silicon controlled rectifier and a thermally compensating resistor connected to said silicon controlled rectifier.

16. A power-source actuated flash device for a camera, comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said detector circuit including an indicator for displaying illumination intensity, said indicator being a' lamp, said compensating means being connected to thermally compensate the level of illumination indicated by the lamp.

17. A device as in claim 16, wherein said indicator comprises a plurality of lamps, said detector circuit including illuminating means for illuminating one of said lamps, said compensating means being connected to said illuminating means for thermally compensating for the illumination of the illuminated lamp.

18. A power-source actuated flash device for a camera, comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said detector circuit comprising an indicator for indicating illumination intensity, said compensating means including a thermally deformable element coupled to said indicator.

19. A photographic system, comprising a camera, circuit means including a main capacitor to be charged by the power source in a flash lamp as well as a flash circuit responsive to said capacitor for'illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said camera having an exposure control, said detector circuit being operationally coupled with said exposure control.

20. A system as in claim 19 wherein said detector circuit is connected with said capacitor to detect the charge stored across said capacitor.

21. A system as in claim 19 wherein said detector circuit includes an indicator for indicating the illumination intensity and an adjustable member, said adjustable member being adjusted in accordance with the indication of the indicator.

22. A system as in claim 21 wherein said indicator effects the adjustment of the adjustable member. 

1. A flash device for a camera comprising a flash circuit including a main capacitor to store illumination energy and a discharge tube which illuminates in correspondence to the amount of illumination energy stored in the main capacitor, and indicator means coupled to said circuit for indicating the amount of the illumination of the discharge tube, said indicator means including compensating means varying in value according to the variation in the energy storing capability of said capacitor in response to an ambient condition and varying the indication of said indicator means on the basis of the ambient condition.
 2. A device as in claim 1, wherein said value varies in response to temperature and said compensating means includes a temperature compensating element.
 3. A device as in claim 1, wherein said indicating means includes means for detecting the illumination of energy charged across the main capacitor and an indicator, and wherein said compensating means is coupled between said detecting means and said indicator.
 4. A device as in claim 1, wherein said indicating means includes a dial and a pointer, said compensating means includes a thermally deformable element, said indicating means connecting said compensating means to said dial and pointer for changing the positions of the dial and the pointer in correspondence with variation of atmospheric temperatures.
 5. An apparatus as in claim 1, wherein said indicating means includes detecting means having a semiconductor element, and said compensating means includes a thermally compensating resistor coupled to said semiconductor element.
 6. A device as in claim 5, wherein said semi-conductor element is a transistor connected to said resistor.
 7. A device as in claim 5, wherein said semi-conductor element is a silicon controlled rectifier connected to said thermally compensating resistor.
 8. A device as in claim 5, wherein said indicating means includes a current meter, said compensating means being connected to said current meter so as thermally to compensate for the reading of said current meter.
 9. A device as in claim 5, wherein said indicating means includes a lamp, the operation of said lamp being thermally compensated by said compensating means.
 10. A device as in claim 9 wherein said indicating means includes a plurality of lamps, said indicating means including illuminating means for illuminating the lamps, said compensating means being connected to said illuminating means for varying the illumination of said lamps on the basis of thermal compensation.
 11. A photographic system, comprising a flash circuit including a main capacitor to store illumination energy and a discharge tube which illuminates in correspondence to the amount of the illumination energy stored in said capacitor, indicating means coupled to said circuit for indicating the amount of the illumination of the discharge tube, and thermal compensating means coupled to said main capacitor and said indicating means to vary in value according to variation in temperature at the same rate as the temperature of said capacitor varies, a camera having exposure control means, said exposure control means being coupled to said indicating means to react therewith.
 12. A photographic system comprising a main capacitor to store illumination energy, a flash circuit including a discharge tube which illuminates in correspondence to the amount of illumination energy stored in the main capacitor, a detecting circuit for detecting the terminal voltage Of said capacitor, a camera, an exposure control circuit in the camera connected to said detecting circuit, and compensating means for compensating for changes in illumination energy stored in the capacitor due to changes in atmospheric temperature, said compensating means being connected to said detecting circuit.
 13. A photographic system as in claim 12 wherein said exposure control circuit includes an adjustable member, said adjustable member being coupled to said detecting circuit.
 14. A power-source actuated flash device for a camera, comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable valve in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said compensating means including a transistor and a thermally compensating resistor connected therewith.
 15. A power-source actuated flash device for a camera, comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said compensating means including a silicon controlled rectifier and a thermally compensating resistor connected to said silicon controlled rectifier.
 16. A power-source actuated flash device for a camera, comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said detector circuit including an indicator for displaying illumination intensity, said indicator being a lamp, said compensating means being connected to thermally compensate the level of illumination indicated by the lamp.
 17. A device as in claim 16, wherein said indicator comprises a plurality of lamps, said detector circuit including illuminating means for illuminating one of said lamps, said compensating means being connected to said illuminating means for thermally compensating for the illumination of the illuminated lamp.
 18. A power-source actuated flash device for a camera, comprising circuit means including a main capacitor to be charged by the power source and a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energy applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said detector circuit comprising an indicator for indicating illumination intensity, said compensating means including a thermally deformable element coupled to said indicator.
 19. A photographic system, comprising a camera, circuit means including a main capacitor to be charged by the power source in a flash lamp as well as a flash circuit responsive to said capacitor for illumination of said flash lamp, and a detector circuit coupled to said circuit means for responding to a thermally variable value in said circuit means corresponding to the illumination energY applied to the lamp, said detector circuit including compensating means for compensating for the thermal variations in the value, said camera having an exposure control, said detector circuit being operationally coupled with said exposure control.
 20. A system as in claim 19 wherein said detector circuit is connected with said capacitor to detect the charge stored across said capacitor.
 21. A system as in claim 19 wherein said detector circuit includes an indicator for indicating the illumination intensity and an adjustable member, said adjustable member being adjusted in accordance with the indication of the indicator.
 22. A system as in claim 21 wherein said indicator effects the adjustment of the adjustable member. 